This is probably something that’s already been said but just in case,
One of the most amazing study tips I have discovered recently is keeping a notebook and pencil RIGHT next to you while you are studying or reading a book for a class (or doing any sort of reading that isn’t just for fun). Every time a stray thought comes to you, write that shit down. Then it isn’t bugging your brain to try and remember for later, it’s there for you to visit when you aren’t studying and you can move past it and go back to study.
Also, make sure it’s a notebook separate to where you keep your notes for studying/classes, so you can keep the two mindsets apart: study / free time. I really like the little ones from Typo for outside thoughts and use big A4 notebooks for my uni notes.
Trust me, as a writer who gets random story/concept tidbits ALL the time, this is amazingly helpful because it ensures I get to keep all the ideas without them clogging up my brainspace, and it also gives me a sort of “reward” for studying, because I have these little brain bits that I get to explore in detail more once I’ve done my allotted school stuff, without feeling guilty for getting off track by delving into them as soon as they come to mind and getting distracted from my studies because I can’t stop thinking about this rad idea.
TL;DR: Keep a spare notebook to write down all of the distracting thoughts that pop up while you’re studying. Write them down, get them out of your brain, go back to studying with the knowledge that they are right there to dedicate brainspace on when you are finished focusing on study.
This is also super useful to lessen anxiety because you are no longer thinking “oh gosh I need to remember these 2 thousand things!!!!”
Thanks @sushiforensics